Ciphertext is information that has been encrypted through a cipher and is no longer readable. Before it has been encrypted, it is called plaintext.

Crack

The process of deciphering information without needing the key or by guessing the key. In cryptography, the goal is to make ciphers that are uncrackable.

Decrypt

The act of deciphering information to its original plainly readable form through the use of a key.

Defeat

The act of circumventing a system to get secret information. This can include cracking a cipher, obtaining keys through theft or subterfuge, or any other manner.

Encrypt

The act of enciphering information so that it cannot be plainly read without first decrypting it using a key.

Hash

The result of putting information through a hash function.

Hash Function

A algorithm that converts an arbitrary amount of information into a fixed-length of information called a hash. Hash functions are one-way so the original information cannot be recovered from the hash.

Key

The information necessary to decrypt information that has been encrypted. This is different than a password which is an easily-remembered piece of information that is usually converted into a key.

Lookup Attack

An attack which uses a premade list to defeat a cipher, examples include a Dictionary Attack and a Rainbow Attack. Lookup attacks are often defeated by using a salt.

Man In the Middle Attack

An attack where someone intercepts an encrypted message, and replaces it with a different message.

Nonce

A one-time random salt used to prevent a attacks like a Replay Attack.

Password

A password is a piece of information that can be remembered which is used to generate a key to decrypt ciphertext.

Plaintext

Plaintext refers to readable information before it has been encrypted. Once plaintext has been encrypted, it becomes ciphertext.

Private Key

A key that must only be known to the sender and recipient in order for the encryption to be secure. Most traditional ciphers use a private key.

Pseudorandom

Something that appears random, but isn't. Most values generated by computers are actually pseudorandom rather than random.

Public Key

A key that is made public, and can be used to encrypt plaintext into ciphertext that can only be decrypted with a private key.

Public Key Encryption

A form of encryption where a public key is generated from a private key. The public key is made freely available, and when plaintext is encrypted, it should only be able to be decrypted with the private key.

Random

A produced value that cannot be predicted. Random values are extremely difficult to produce, and are usually pseudorandom.

Salt

Information added to plaintext before being hashed or encrypted to help prevent lookup attacks.

Symmetric Key Algorithms

Those ciphers that can be encrypted and decrypted with the same key. Most traditional ciphers use a symmetric key algorithm.

Trapdoor Function

A mathematical function that is easy to compute one-way, but difficult to compute in reverse. Trapdoor functions are found in asymmetric key algorithms for public key encryption.